Corrugated solder pre-form and method of use

ABSTRACT

A solder pre-form for soldering a coaxial cable to a connector body is provided with a plurality of flux grooves on a cable side and a connector side. The solder pre-form may also have a plurality of holes between the cable and connector sides. In a method of use, flux is applied to the flux grooves and the solder pre-form applied to encircle the outer conductor which is then inserted into the connector body and the solder pre-form melted to complete the solder interconnection. Where holes are present, flux may be applied to the connector side, passing through the holes also to the cable side.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §120 to U.S.application Ser. No. 14/110,538, filed Nov. 14, 2013, which itself is a35 U.S.C. §371 national stage application of PCT InternationalApplication No. PCT/US2012/024000, filed on Feb. 6, 2012 which in turnclaims priority from U.S. application Ser. No. 13/084,136, filed Apr.11, 2011, the entire contents of each of which are incorporated byreference herein in their entirety.

BACKGROUND OF THE INVENTION

This invention relates to a solder pre-form. More specifically, theinvention relates to a solder pre-form with improved flux applicationand distribution characteristics for soldering a coaxial connector tothe outer conductor of a coaxial cable.

DESCRIPTION OF RELATED ART

Coaxial cables and coaxial connectors are used, for example, incommunication systems requiring a high level of precision andreliability. To create a reliable and cost efficient electro-mechanicalinterconnection between the coaxial cable and the coaxial connector, itis often desirable to interconnect the cable and connector viasoldering.

Solder pre-forms may be utilized to improve interconnection quality whensoldering coaxial connectors to coaxial cables. The use of a solderpre-form standardizes the location and amount of solder applied.Representative of this technology is commonly owned U.S. Pat. No.5,802,710 issued Sep. 8, 1998 to Bufanda et al (Bufanda). Bufandadiscloses a solder pre-form with a planar connector side (outer surface)and a cable side (inner surface) dimensioned to key with corrugations ofan annular corrugated outer conductor. Other solder pre-forms, forexample for soldering a coaxial connector with a smooth sidewall outerconductor coaxial cable, have been provided as a plurality of annularrings and/or a cylindrical tube.

Aluminum material exposed to air quickly oxidizes, forming an aluminumoxide coating that interferes with solder bonding. Special aluminummaterial specific soldering flux with a heat activated high acid contentmay be used to prepare aluminum material surfaces for soldering.However, such flux may be difficult to apply evenly within theinterconnection area.

Therefore, it is an object of the invention to provide a solder pre-formand method of use that overcomes deficiencies in such prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description of the embodiments given below, serve toexplain the principles of the invention.

FIG. 1 is a schematic isometric view of a solder pre-form.

FIG. 2 is a schematic isometric view of the solder pre-form of FIG. 1bent into a U-shape.

FIG. 3 is a schematic isometric view of the solder pre-form of FIG. 2with a coaxial cable seated within the solder pre-form.

FIG. 4 is a schematic isometric view of the solder pre-form of FIG. 3after bending into an annulus for enclosing the outer diameter of theouter conductor of a prepared end of a coaxial cable.

FIG. 5 is a schematic isometric view of an embodiment of a solderpre-form with flux grooves perpendicular to a longitudinal axis of thesolder pre-form.

FIG. 6 is a schematic isometric view of the solder pre-form of FIG. 5bent for enclosing a prepared end of a coaxial cable.

FIG. 7 is a schematic isometric partial cutaway view of the solderpre-form of FIG. 5 flux coated and seated upon the outer conductor,inserted within the connector body bore for soldering the coaxialconnector to the coaxial cable.

FIG. 8 is a schematic isometric view of an embodiment of a solderpre-form with rectangular holes.

FIG. 9 is a schematic isometric view of the solder pre-form of FIG. 8bent into a U-shape.

FIG. 10 is a schematic front view of an embodiment of a solder pre-formwith round holes.

FIG. 11 is a schematic isometric view of the solder pre-form of FIG. 10bent into a U-shape.

FIG. 12 is a schematic isometric view of the solder pre-form of FIG. 11bent for enclosing a prepared end of a coaxial cable.

FIG. 13 is a schematic isometric view of the solder pre-form of FIG. 1enclosing a prepared end of a coaxial cable.

FIG. 14 is a schematic isometric view of the solder pre-form of FIG. 1enclosing a prepared end of a coaxial cable prior to insertion into acoaxial connector.

FIG. 15 is a schematic cross-section side view of the solder pre-form ofFIG. 1 coupled between a coaxial connector and a coaxial cable prior tosoldering.

FIG. 16 is a schematic isometric partial cutaway cross-section view ofthe solder pre-form of FIG. 1 coupled between a coaxial connector and acoaxial cable after soldering.

FIG. 17 is a schematic isometric partial cutaway view of the solderpre-form of FIG. 10 enclosing a coaxial cable.

FIG. 18 is a schematic isometric partial cutaway view of the solderpre-form of FIG. 10 coupled between a coaxial connector and a coaxialcable prior to soldering.

DETAILED DESCRIPTION

The inventor has recognized that significant difficulties arise whenattempting to solder a coaxial connector to a smooth sidewall outerconductor coaxial cable when the connector body and/or coaxial cableouter conductor are aluminum material.

The inventor's analysis indicates that, due to the speed of the aluminumoxide coating formation, if the aluminum material surfaces to besoldered are not coated with the flux immediately prior to initiation ofheating to melt the solder pre-form, the quality of the resulting solderinterconnection may be degraded. When the flux is heated as soldering isinitiated, the flux volatizes, wetting and acid washing away thealuminum oxide coating likely present on the aluminum material surfaces,immediately prior to the melting of the solder pre-form to solder thesesurfaces together.

When utilizing the prior solder pre-forms, for example with a smoothconnector side or multiple solder pre-form ring configuration,inventor's testing has shown that during insertion of the prepared endof the coaxial cable into the connector body bore any flux that may bepresent on the connector side of the solder pre-form and/or that mayhave been manually applied to the connector body bore may be partiallyor entirely scraped off. Thereby, the flux is prevented from acting uponthe aluminum oxide coatings on the aluminum material surfacesimmediately prior to melting of the solder pre-form during the solderprocedure resulting in degraded solder interconnection quality. Inparticular, circumferential uniformity of the solder joint around theinner diameter of the connector body bore and/or outer diameter of theouter conductor may be degraded, which can be a significantcharacteristic of interconnection quality for high frequencyapplications.

The inventor has recognized that flux may be retained proximate theinterconnection surfaces during cable end insertion into the connectorbody bore by providing a solder pre-form with flux grooves on both sidesof the solder pre-form. The inventor has also recognized that theretention and flow of flux within the interconnection area may befurther facilitated by providing the solder pre-form with holes,enabling a method of use in which flux application by the operator isonly required with respect to the connector side of the solder pre-form.

A first exemplary embodiment of a solder pre-form 2 for soldering aconnector body 4 of a coaxial connector 6 with an outer conductor 8 of aprepared end 10 of a coaxial cable 12 is shown in FIGS. 1-3. The solderpre-form 2 may be provided as a planar sheet, as shown in FIG. 1.Alternatively, to facilitate wrapping accuracy and/or uniformity of thesolder pre-form fit around the outer conductor 8 of the coaxial cable12, the solder pre-form 2 may be provided formed as a U-shaped unit, forexample as shown in FIG. 2. The U-shape is dimensioned to cradle theouter diameter of the coaxial cable 12 within the base 13 of theU-shape, as shown in FIG. 3. When the first and second ends of thepre-form 2 ends are bent towards one another around the outer conductor8, for example with a hand tool such as pliers customized for a specificdesired diameter and/or flux groove 14 configuration, the solderpre-form 2 encircles the outer conductor 8 as shown for example in FIG.4.

The solder pre-form 2 is provided with a plurality of flux grooves 14 ona cable side 16 and a connector side 18. The flux grooves 14 areoperable for receiving and retaining viscous flux 20 during pre-assemblyand insertion of the coaxial cable 12 into a connector body bore 21 ofthe connector body 4. The flux grooves 14 may be applied orientedparallel to a longitudinal axis of the solder pre-form 2, as best shownin FIGS. 1, 8 and 10, for seating upon the outer conductor 8perpendicular to a longitudinal axis of the coaxial cable 12.Alternatively, the flux grooves 14 may be applied, for example, orientedperpendicular to a longitudinal axis of the solder pre-form 2 forseating upon the outer conductor 8 parallel to a longitudinal axis ofthe coaxial cable 12, for example as shown in FIGS. 5-7.

The flux grooves 14 on the cable side 16 and the flux grooves 14 on theconnector side 18 may be provided, for example, by forming corrugationsthrough a cross section of the solder pre-form 2 providing correspondingflux grooves 14 on each side. Thus, each flux groove 14 on the connectorside 18 will be a trough corresponding to a crest on the cable side 16and each flux groove 14 on the cable side 16 will be a troughcorresponding to a crest on the connector side 18. Such corrugations maybe formed by, for example, stamping, rolling and/or extruding theselected solder material.

One skilled in the art will appreciate that, when the flux grooves 14are applied perpendicular to the longitudinal axis of the coaxial cable12, a low viscosity flux 20 thereon may be temporarily retained thereinwhile the coaxial cable is oriented vertically prior to soldering.Similarly, where the flux grooves 14 are oriented parallel to thecoaxial cable 12 longitudinal axis a higher viscosity flux 20 may beretained and a direct vertical path is provided for egress of thevolatized flux 20 out of the connector body bore 21 (see FIG. 6) asheating is initiated.

In further embodiments, as shown for example in FIGS. 8-12, the solderpre-form 2 may be provided with a plurality of holes 22 to allow flux 20to pass from the connector side 18 to the cable side 16. The holes 22may, for example, be slots, as in FIGS. 8 and 9, or circular, as inFIGS. 10-12. The holes 22 provide communication between the connectorside 18 and the cable side 16, whereby flux 20 applied to the connectorside 18 also passes through the holes 22 to also fill the flux grooves14 on the cable side. As the holes 22 enable flux 20 passage from theconnector side 18 to the cable side 16, manual application of flux 20 tothe flux grooves 14 of the connector side 18 prior to encircling theouter conductor 8 with the solder pre-form 2 may be eliminated, forexample as shown in FIGS. 17 and 18. Without the need for applying theflux 20 directly to the connector side 16, the pre-form 2 may besupplied pre-formed in an annular configuration as shown for example inFIG. 12 to further simplify and/or eliminate a step of bending of thesolder pre-form 2 around the outer conductor 8 during pre-assembly. Toincrease the solder pre-form solder volume while maintaining theconnector side to cable side flux transmission functionality, the holes20 may be formed as slots oriented normal to the solder pre-formlongitudinal axis (see FIGS. 8 and 9).

Similarly, one or more holes 22 may be positioned along sidewalls of theflux grooves 14 to form an egress path through the solder pre-form 2 forthe volatized flux between each flux groove 14 and out of the connectorbody bore 21 during initial heating of the soldering procedure, whichmay reduce the generation of flux 20 and/or air pockets and theassociated entrapment and/or sputtering of such through molten solderduring soldering.

In an exemplary method using the solder pre-form 2 of the firstembodiment, a coaxial cable 12 with a smooth outer conductor 8 issoldered with a connector body 4, for example wherein the connector body4 and/or the smooth sidewall outer conductor 8 are each made of aluminummaterial. Aluminum material may be aluminum, aluminum alloy or a surfacecoating of aluminum or aluminum alloy.

The flux grooves 14 on a cable side 16 of a U-shaped solder pre-form 2are filled with flux 20, for example as shown in FIG. 3. The first andsecond ends of the solder pre-form 2 are bent toward each other toenclose the outer diameter of the outer conductor 8 of a prepared end 10of a coaxial cable 12, for example as shown in FIG. 4. An inner contact23, insulator 24 and/or disc 26 may be coupled with the prepared end 10of the coaxial cable 12, for example as shown in FIG. 13. Specifically,the inner contact 23, carrying the insulator 24 and disc 26, may becoupled with the inner conductor 28 via, for example, inward-biasedspring contacts of the inner contact 23 and/or a further solderprocedure between the inner contact 23 and the inner conductor 28.

The plurality of flux grooves 14 on the connector side 18 are filledwith flux 20, for example as shown in FIG. 14. The coaxial cable 12coupled with the solder pre-form 2 is then inserted into the connectorbody bore 21 of the connector body 4, for example as shown in FIG. 15.The combined connector body 4 and coaxial cable 13 may be securely heldvertically, with the connector body 4 on the bottom, for example in asoldering apparatus as disclosed in commonly owned U.S. Pat. No.7,900,344 issued Mar. 8, 2011 to Ng et al. Heat is applied to an outersurface of the connector body 4, volatizing the flux 20 and then meltingthe solder perform 2, which pools the solder 30 between the connectorbody bore 21 and the outer conductor 8. Upon cooling, the solderinterconnection is completed, for example as shown in FIG. 16.

As described herein above, because flux applied to the connector side 18can pass through the holes 22 to the connector side 18, a pre-form 2with holes 22 enables elimination of the step of applying flux directlyto the cable side 16, simplifying the method of use. Further, the edgesof the holes 22 may provide a grip surface for enhancing a hold of thesolder pre-form 2 in place upon the outer conductor 8 during verticalinsertion into the connector body bore 21.

Where the solder pre-form 2 is dimensioned to create an interference fitbetween the pre-form 2 and the outer conductor 8, the pre-form 2 gripsthe outer conductor 8 prior to insertion of the prepared end of thecoaxial cable 12, with the solder pre-form 2 attached, into theconnector body bore 21, simplifying the pre-assembly process.

Further, where the corrugation peaks of the connector side of thepre-form 2 also fit with an interference fit against the connector bodybore 21, thermal conductivity through the solder pre-form 2 to the outerconductor 8 is improved, which reduces thermal requirements of thesolder process. Thereby, the possibility of thermal damage to adjacentnon-soldered elements such as the jacket and coaxial cable dielectricinsulation is reduced and the process solderability is improved byreducing the time between the first application of heat (which initiatesflux 20 melting) and then, as heat transfer to and through the solderpre-form 2 increases, melting of the solder 30 which completes thesolder operation. Because the time between flux 20 melting and solder 30melting is reduced when thermal conductivity through the assembly isimproved, there is less chance of all flux 20 being entirely evaporatedand/or burned away from a desired interconnection surface, before thesolder 30 melts.

One skilled in the art will appreciate that a solder pre-form 2according to the invention may improve connector body to outer conductorsolder connection quality, especially where aluminum materials are beingutilized. Thereby, the further adoption of aluminum material use in thecoaxial connector and/or coaxial cable arts is enabled, which in turnmay enable significant material cost savings for connector and coaxialcable manufacturers.

Table of Parts  2 solder pre-form  4 connector body  6 coaxial connector 8 outer conductor 10 prepared end 12 coaxial cable 13 base 14 fluxgrooves 16 cable side 18 connector side 20 flux 21 connector body bore22 hole 23 inner contact 24 insulator 26 disc 28 inner conductor 30solder

Where in the foregoing description reference has been made to ratios,integers or components having known equivalents then such equivalentsare herein incorporated as if individually set forth.

While the present invention has been illustrated by the description ofthe embodiments thereof, and while the embodiments have been describedin considerable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details, representativeapparatus, methods, and illustrative examples shown and described.Accordingly, departures may be made from such details without departurefrom the spirit or scope of applicant's general inventive concept.Further, it is to be appreciated that improvements and/or modificationsmay be made thereto without departing from the scope or spirit of thepresent invention as defined by the following claims.

The invention claimed is:
 1. A method for soldering a coaxial cable witha coaxial connector, comprising the steps of: applying a flux to aplurality of flux grooves of a cable side of a solder pre-form; applyingthe solder pre-form around an outer conductor of the coaxial cable,whereby the solder pre-form at least partially encircles the outerconductor; applying flux to a plurality of flux grooves of a connectorside of the solder pre-form; inserting the coaxial cable with the solderpre-form thereon into a connector body bore of the coaxial connector;and melting the solder pre-form, wherein the solder pre-form includes aplurality of holes; the holes communicating between the cable side andthe connector side.
 2. The method of claim 1, wherein the holes areslots perpendicular to a longitudinal axis of the solder pre-form. 3.The method of claim 1, wherein the flux is viscous in the plurality offlux grooves of the cable side of the solder pre-form during the step ofapplying the solder pre-form around the outer conductor.
 4. The methodof claim 1, wherein the step of applying flux to the plurality of fluxgrooves of the connector side of the solder pre-form occurs after thestep of applying the solder pre-form around the outer conductor of thecoaxial cable.
 5. The method of claim 1, wherein the flux applied to theconnector side of the solder pre-form is viscous during the step ofinserting the coaxial cable with the solder pre-form thereon into theconnector body bore of the coaxial connector.
 6. A method for solderinga coaxial cable with a coaxial connector, comprising the steps of:applying a flux to a plurality of flux grooves of a cable side of asolder pre-form; applying the solder pre-form around an outer conductorof the coaxial cable, whereby the solder pre-form at least partiallyencircles the outer conductor; applying flux to a plurality of fluxgrooves of a connector side of the solder pre-form; inserting thecoaxial cable with the solder pre-form thereon into a connector bodybore of the coaxial connector; and melting the solder pre-form; whereinthe flux is viscous in the plurality of flux grooves of the cable sideof the solder pre-form during the step of applying the solder pre-formaround the outer conductor.
 7. A method for soldering a coaxial cablewith a coaxial connector, comprising the steps of: applying a flux to aplurality of flux grooves of a cable side of a solder pre-form; applyingthe solder pre-form around an outer conductor of the coaxial cable,whereby the solder pre-form at least partially encircles the outerconductor; applying flux to a plurality of flux grooves of a connectorside of the solder pre-form; inserting the coaxial cable with the solderpre-form thereon into a connector body bore of the coaxial connector;and melting the solder pre-form; wherein the flux applied to theconnector side of the solder pre-form is viscous during the step ofinserting the coaxial cable with the solder pre-form thereon into theconnector body bore of the coaxial connector.
 8. A method for solderinga coaxial cable with a coaxial connector, comprising the steps of:applying a flux to a plurality of flux grooves of a cable side of asolder pre-form; applying the solder pre-form around an outer conductorof the coaxial cable, whereby the solder pre-form at least partiallyencircles the outer conductor; applying flux to a plurality of fluxgrooves of a connector side of the solder pre-form; inserting thecoaxial cable with the solder pre-form thereon into a connector bodybore of the coaxial connector; and melting the solder pre-form; whereinthe step of applying flux to the plurality of flux grooves of theconnector side of the solder pre-form occurs after the step of applyingthe solder pre-form around the outer conductor of the coaxial cable. 9.The method of claim 8, wherein the solder pre-form is U-shaped; thesolder pre-form applied to encircle the outer conductor by bending firstand second ends of the solder pre-form towards one another around theouter conductor.
 10. The method of claim 9, wherein the bending isperformed with a hand tool.
 11. The method of claim 8, wherein the outerconductor and the coaxial connector are one of aluminum and aluminumalloy.
 12. The method of claim 8, further including the step ofinstalling an inner contact upon an inner conductor of the coaxialcable.
 13. The method of claim 12, further including the step ofinstalling an insulator onto the inner contact.
 14. The method of claim8, wherein the flux grooves extend along a longitudinal axis of thesolder pre-form.
 15. The method of claim 8, wherein the flux groovesextend perpendicular to a longitudinal axis of the solder pre-form. 16.The method of claim 8, wherein the flux grooves are formed bycorrugations of the solder pre-form.
 17. The method of claim 9, whereina bend radius of the solder pre-form is dimensioned to seat upon anouter diameter of an outer conductor of the coaxial cable.
 18. Themethod of claim 9, wherein a bend radius of the solder pre-form isdimensioned for an interference fit upon an outer diameter of an outerconductor of the coaxial cable.